First round with rust near end

For the last nine months, Alan Blaine hasn’t spent many days when he didn’t think about Asian soybean rust and the havoc it could wreak on Mississippi’s 1.6 million acres of soybeans.

Almost since the day — last Nov. 9 — that soybean rust was first confirmed in the United States, Blaine and other Mid-South Extension specialists have been working to find ways to help producers prevent the potential loss of 10 to 50 percent of their crop to the disease.

Now that the end of the first season of living with the threat is approaching, Blaine says the soybean industry made some good strides toward dealing with rust. And he believes it made some mistakes, too.

“We’ve been sitting on pins and needles on this disease,” Blaine told farmers and industry representatives attending the Mid-South Ag-Technology Field Day at the Memphis, Tenn., Agricenter. “Fortunately, we had several things on our side that kept it from being as devastating as it could have been.”

One was the predominantly hot, dry weather that has been less than ideal for the development of soybean rust spores in the Mid-South. Another was the failure of the disease to overwinter in south Louisiana or Texas where it could have produced spores that might have been blown to the northeast. And there’s the history of the disease.

“In the 102 years since Asian soybean rust was first discovered in China, it has never had a significant impact on any country in the first year,” said Blaine, an Extension agronomist with Mississippi State University. “That’s proving to be the case again.”

Until mid-July, soybean rust was a no-show in the Mid-South. University and Extension specialists had discovered rust spores on kudzu and on soybeans in sentinel plots in Alabama, Florida and Georgia, but nothing east of the Mississippi-Alabama line.

Then, William F. Moore, a retired plant pathologist working with Mississippi State’s Soybean Management by Applied Research and Technology (SMART) Program, found rust spores on two leaves taken from a soybean field in George County in the southeast portion of the state.

The presence of Asian soybean rust spores on the leaves was confirmed on July 13, and the field, which was one of only a handful of fields in George County, was destroyed the next day.

“It took someone as good as Billy Moore to find the disease in those fields,” said Blaine. “Most people would have never seen it.”

Since then, more rust infections have been confirmed in Colquitt County in south central Georgia, bringing to four the number of counties in that state where soybean rust spores or infections have been found.

Soybean rust has also been confirmed in eight counties in Florida, including the first discovery — in kudzu on Feb. 22 — in the United States in 2005, an indication that disease spores did overwinter in the central portion of that state.

The response to that discovery could be one of the miscues that Blaine was speaking of.

“I believe we made a mistake in not destroying those fields,” he said. “I think now that we should have taken an eradication approach and wiped it out in those counties.”

After the first confirmation in Pasco County in west central Florida, the field was allowed to sit undisturbed for 60 days, he noted. A similar situation occurred in Baldwin County on the Alabama Gulf Coast in June.

“They found rust in a sentinel plot just outside of Foley, Ala.,” he said. “Then, two weeks later, they found it in a commercial soybean field about two miles north of the initial area. They said that when you shook the plants in that area of the field, a red cloud came out of the canopy. They would have been better off to get rid of it.”

As evidenced by the discovery in the field in George County, an area with few acres of soybeans, Mississippi Extension agents and consultants haven’t found soybean rust for lack of trying.

“We started planting sentinel plots in south Mississippi on Feb. 17 and finished the last one — No. 20 — on March 18,” he said. “We had a plot of Group 5.5 soybeans planted in February in Tylertown, right on the border with Louisiana, that are some of the best-looking soybeans I’ve seen.

“I don’t think we have scratched the surface on what we can do with soybeans planted in February and March in Mississippi.”

Blaine says he’s also come to the conclusion that Mississippi farmers need to spray their soybeans with a fungicide for rust or other plant diseases when they reach the R1 or flowering stage of development.

“You cannot scout for this disease,” he said. “We had an expert from South Africa visit us. He pulled four samples and was convinced soybean rust was on three of the leaves. All three of those came back negative. I told him, ‘If you can’t find it, I know I can’t.’”

The agronomist said Mississippi State specialists have records on 138 fields in the SMART program that recorded a 5-bushel-per-acre or higher yield increase when fungicides were applied. “That’s enough to pay for a total soybean rust program,” he noted. “We need to apply a fungicide early that will help with other diseases and help protect against rust.

“This is really a plant health issue. Melvin Newman, the soybean plant pathologist in west Tennessee, has more data than anyone else showing that the improvement in plant health will offset the cost of the fungicide.”

Blaine said he wasn’t trying to discourage growers from scouting for soybean rust. “I’m not saying you can’t do it, but I’ve seen the experts miss it.

“Applying fungicides will make you a better producer,” he said. “I know growers are really looking at their crops this year. I’ve had calls from them telling me they think they have soybean rust when I knew they probably didn’t. But they’re getting out and checking fields.”

The Ag-Technology Field Day attracted about 400 farmers plus consultants and industry representatives, many who came to look at soybean fields and hear Blaine talk about Asian soybean rust. The tour included 13 stops conducted by a virtual who’s who of Mid-South crop input suppliers.

“We played the game and won this year,” said Blaine, expressing his belief that many Mid-South growers will soon be past the point where rust could reduce their yields. “But we won’t win every year. Hopefully, we’ll learn more on what to do about it before it shows up in full force.”